Question

which of the following affects the shape and amplitude of the recorded emg signal
the direction the muscle fiber action potential travels thru the recording zone
the distance the muscle fiber action potential travels from active fibers to the recording electrodes
the horizontal distance the muscle fiber action potential travels along the muscle fiber
a, b and c above are all correct
none of the above

Explanation:

• The direction of muscle fiber action potential travel through the recording zone affects the signal's shape due to the spatial - temporal summation and orientation - related electrical field changes.
• The distance from active fibers to recording electrodes impacts amplitude (as the signal attenuates with distance following the inverse - square law for electrical fields in a homogeneous medium conceptually, similar to how a weaker signal is received from a farther source).
• The horizontal distance along the muscle fiber also affects as it relates to the propagation of the action potential and how it is sampled by the recording electrodes in terms of its waveform.

Answer:

a, b and c above are all correct